1. Field of the Invention
This invention relates to a video signal processing system, and more particularly to a video signal processing system arranged to interpolate scanning lines and/or to compensate for a drop-out.
2. Description of the Prior Art
In processing a video signal, and particularly a reproduced video signal, it is necessary to have, as well known, some means for compensating defective parts of the signal which are called "drop-out". Further, in cases where a one frame portion of (two field portion) of a signal is to be simulatively obtained from one field portion of a signal in particular, it is necessary to carry out an operation called "scanning line interpolation".
In the case of a video print system, for example, it is hardly possible to print at real time, as a considerable length of time is required for printing one picture frame. Therefore, one picture portion of the input video signal is recorded or stored either in a record bearing medium such as a magnetic disc or the like or in a storage medium such as a semi-conductor memory or storage, and a printing operation is carried out by reproducing the recorded or stored signal. In such a case, drop-outs tend to occur in the reproduced signal thus obtained. In order to obtain an adequate printed picture, therefore, some means for compensating the drop-cuts becomes indispensable. Further, while a video print system is arranged to obtain a still picture, one frame signal is composed of two field portions of the signal which deviate one field period of time from each other. In order to obtain a printed picture without any blur, therefore, it is preferable to use only one field portion of the signal. However, in the event of only one field portion of signal, a picture of high quality is hardly obtainable because of a fewer number of scanning lines. In that case, therefore, the number of scanning lines must be increased by a scanning line interpolating operation.
A video signal processing system of that kind necessitates use of many delay circuits for scanning line interpolation and drop-out compensation. For these delay circuits, analog delay lines, such as glass lines, CCD delay lines, etc., are generally employed. However, these analog delay lines tend to cause signal deterioration and also changes in characteristic due to variations in ambient temperature. Further, with respect to the drop-out compensation, the quality of the picture tends to degrade in the compensated parts as each of the defective parts of the signal is merely replaced with a signal portion preceding it by an extent corresponding to one or several lines.
Further, the conventional arrangement for interpolating the scanning lines of a chrominance signal is capable of interpolating only for one field portion. However, an arrangement to increase this limited interpolation capability to a 2 or 3 field portion would necessitate use of a greater number of delay lines and would makes the above-stated problems more salient. Besides, such arrangement would result in an extremely complex processing system.